To protect the public from
the human equivalent of "mad cow disease," U.S. Food and Drug Administration
(FDA) authorities have announced an indefinite ban on blood donations from
persons who spent six months or more in the United Kingdom (U.K.) since
1980. Experts estimate that the ban will reduce the pool of current donors
by up to 2.2%, placing additional pressure on availability of blood products.

Transmissible spongiform
encephalopathies (TSE) are chronic, progressive, and 100% fatal neurodegenerative
disorders that occur in both humans and animals, which require long incubation
periods for disease expression. Bovine spongiform encephalopathy (BSE),
or "mad cow disease," is largely transmitted by feeding animals with meat
and bonemeal derived from BSE-infected cattle and sheep. Creutzfeldt-Jakob
disease (CJD) is among the TSEs that affect humans. In 1996, a "new variant"
of CJD (nv-CJD) was reported in persons in the U.K., which was believed
to have been transmitted by human consumption of meat from BSE-infected
cattle. As a result, some scientists have suggested that no ruminant-derived
products at all should be fed to animals intended for human consumption.

A recent report of the Council
on Scientific Affairs of the American Medical Association (AMA) suggests
that the emergence of nv-CJD in Britain was due to distinctive circumstances
not found in the U.S. The report concludes that current risk of transmission
of BSE in the U.S. is minimal because (1) BSE has not been shown to exist
in the U.S.; (2) adequate regulations exist to prevent both entry of foreign
animals into the U.S. and uncontrolled amplification of disease within
the U.S. cattle population; and (3) adequate guidelines exist to prevent
bovine materials from contaminating products intended for human consumption.

The FDA has banned the feeding
to cattle or sheep almost any substance containing meat, bones, or fat
of mammals other than pigs and horses (who are believed not to be susceptible
to TSEs). However, issues of questionable enforcement of these guidelines
have been raised by critics who note that the FDA has allocated the equivalent
of only 17 full-time inspectors nationwide to the 14,000 facilities currently
involved in feed production and rendering. Thus in large part, the absence
of ruminant byproducts in animal feed relies on the honesty of feed producers.
Under such circumstances, possible financial incentives to include prohibited
materials in feed could be an important factor. Careful monitoring of the
constituents of animal feed are critical for effectively preventing TSE-contaminated
materials from reaching the human food supply.

While the FDA is appropriately
erring on the side of caution in attempting to eliminate TSEs from the
food chain, the effect will be a reduction in available blood supplies.
A delicate balancing act will ensue between ensuring TSE-free food while
maintaining the integrity of the blood supply. Accordingly, both the private
and public sectors should make concerted efforts to increase the number
of blood donors in order to moderate the impact of reduction in donations
from the British donor ban.